Conventionally, a chrome plated steel plate is used for a speaker frame, and various speaker components are bonded to the speaker frame by using an adhesive.
A vibration plate (hereinafter referred to as a cone) is bonded to the speaker frame via an edge.
When the edge is formed with a compression molded foamed urethane or an ethylene-vinyl-acetate-copolymer to increase mechanical strength, a water base synthetic chloroprene rubber adhesive or a water base SBR (styrene-butadiene-copolymer-rubber) adhesive are used for bonding the edge to the frame because those edge materials are soluble or swelled in a solvent based adhesive.
On the other hand, when the edge is formed with a kind of rubber such as natural SBR, EPDM (ethylene-propylene-diene-rubber) or the like, a solvent base synthetic chloroprene rubber adhesive, a water base synthetic chloroprene rubber adhesive, a solvent base SBR adhesive or a water base SBR adhesive is used.
In general, the adhesive is selected taking adhesion, influence on the materials, cost and production efficiency into account.
When the cone is directly bonded to the speaker frame the adhesive is selected in the same manner as described above in general.
When a damper is bonded to the speaker frame, a solvent base synthetic chloroprene rubber adhesive is generally used because the damper is formed with phenol-resin-impregnated cloth.
For bonding a top plate to the speaker frame, a solvent base synthetic chloroprene rubber adhesive is generally used because the top plate is formed with a metal plate.
In recent years, however, from the viewpoint of recycling for the protection of environment and for decreasing the weight of a speaker, polypropylene has come to be used for the speaker frame. In this case, the conventional adhesives described above have not sufficient adhesion to the polypropylene speaker frame, i.e., the conventional adhesives have not sufficient bonding strength for producing a speaker having a polypropylene frame.
The present invention aims to provide a synthetic chloroprene rubber adhesive composition that is superior in bonding various components to the components formed with polypropylene as described above, also aims to provide a process for producing a speaker by using the adhesive composition.